/ # I like to use tilde as the "delimiter" for this regex pattern


# start character class definition
[
    # one character between a to z.
    a-z
# end character class definition
]


# start character class definition
[
    # immediately followed by 1 character between a to z, or 0 to 9.
    a-z0-9
# end character class definition
]


# start character class definition
[
    # immediately followed by   "1 or more"   characters between 0 to 9.
    0-9
]
# one or more of the preceding token.
+


# delimiter is the tilde symbol -- Useful for pretty sexy regex. Doesnt that make you feel hot?
# the letter "x" is a flag for PCRE_EXTENDED. http://php.net/manual/en/reference.pcre.pattern.modifiers.php
/x